Novel perfluorinated polyethers and process for their preparation

ABSTRACT

Perfluorinated polyethers having the formula 
     
         R.sub.f O--(CF.sub.2 CF.sub.2 O).sub.n --R&#39;.sub.f 
    
     wherein n is and integer of 1-11 and each of R f  and R&#39; f  is a perfluorinated C 1  -C 5  -alkyl radical, dimers of such polyethers and carbon to carbon intramolecularly coupled cyclic derivatives of such polyethers are produced by direct fluorination of the polyethers in an inert solvent. Compositions of the perfluorinated polyethers and their derivatives are useful as functional fluids.

This is a division of patent application Ser. No. 07/150,963, filed Jan.29, 1989.

BACKGROUND OF THE INVENTION

I Field of the Invention

The present invention relates to new polymeric products of high puritywhose molecules consist essentially of carbon, fluorine, and oxygen andhaving a polyether structure and to a new process for preparing the sameby directly fluorinating the corresponding polyether consistingessentially of carbon, hydrogen, and oxygen in a solvent. Moreparticularly, the present invention relates to perfluorinated polyethersconsisting of about one to eleven --(CF₂ CF₂ O) repeating unitsterminated with perfluorinated C₁ -C₅ alkyl radicals and to a newprocess for preparing the same by directly fluorinating thecorresponding polyether in an inert solvent.

II Description of the Prior Art

Certain organofluoro compounds and polymers are known to exhibitoutstanding high temperature stability properties and chemicalinertness. Organofluoro compounds containing only carbon and fluorineatoms, fluorocarbon ethers and fluorocarbon amines are three generalclasses of materials which have found commercial success as coolants,lubricants, heat-transfer agents in reflow condensation solderingprocesses, and other functional fluid uses. Many compounds can be fullyand directly chlorinated or brominated. However, when such compounds aredirectly fluorinated considerable difficulties are encountered.

Because perfluorinated polyethers have desirable properties, such asextremely good heat stability, outstanding chemical inertness, excellentlubricating properties and the like, much effort has been made toprepare perfluorinated polyethylene oxide having perfluoroalkyl terminalgroups. Limited success has been reported in preparing suchperfluorinated polymers having a low number (i.e., 2-4) of repeatingethylene oxide units and in preparing such perfluorinated polymershaving a high molecular weight. For example, when high molecularpolyethylene oxides are perfluorinated, most of the resulting product isa high molecular weight solid with only a small amount of low molecularweight fluid being formed. In order to prepare perfluorinated polyethersof mid-range molecular weights, i.e. being composed of 4-11perfluoroethylene oxide units, it has been suggested to break solidperfluoro polyethers of high molecular weight into low molecular weightfragments by means of pyrolyzing the perfluoro polyethers at extremelyhigh temperatures of 500-600° C. and collecting the vaporized lowermolecular weight perfluoro polyether fluids. The pyrolysis is not onlyexpensive and difficult to carry out but also the resulting fluids arerandom mixtures of many perfluoro polyethers because of the randomnature of the bond breakage of the high molecular weight perfluoropolyethers. The fragments must be reacted with fluorine gas to eliminateacyl end groups and any unsaturation of the resulting perfluoropolyethers.

Efforts to provide a process for the direct fluorination of organiccompounds in solvents have heretofore been fraught with many problems,including the breakdown of the solvent by the fluorine gas, formation ofexplosive mixtures, and the insolubility of the fluorine gas with thesolvent.

SUMMARY OF THE PRESENT INVENTION

The present invention provides a process for direct and fullfluorination of linear polyethylene oxide ethers in a solvent. Theperfluorinated polyethylene oxide ethers are characterized by theformula

    R.sub.f O--(CF.sub.2 CF.sub.2 O).sub.n --R'.sub.f

wherein n is an integer from 1-11 and include dimers and cycliccompounds thereof resulting from intramolecular carbon to carboncoupling. The R_(f) and R'_(f) radicals which may be the same ordifferent radicals are perfluorinated C₁ -C₅ alkyls, includingperfluoromethyl, perfluoroethyl, perfluoropropyl, perfluoroisopropyl,perfluorobutyl, perfluoroisobutyl, and perfluoro-t-butyl. The preferredperfluorinated polyethylene oxides have a molecular weight of about250-2000 and boil above 130° C.

In accordance with the process aspect of the present invention apolyether having the following formula is produced by conventionalprocedures

    RO--(CH.sub.2 CH.sub.2 O).sub.n --R'

wherein n is an integer of 1-11 and preferably an integer of 5-8. Eachof R and R' is a C₁ -C₅ alkyl radical independently selected frommethyl, ethyl, propyl, isopropyl, butyl, isobutyl, t-butyl, etc. Thepolyether is dissolved in a suitable chemically inert fluorocarbonfluid. The preferred solvent is 1,1,2-trichloro-1,2,2-trifluoroethane.The solvent should not only be chemically inert in respect to reactantsand products, it should also be free of contaminants, such as iron andnickel fluorides that would catalyze a reaction between the fluorine gasand the solvent resulting in the decomposition of the solvent. Gaseousfluorine is introduced into the solvent containing the polyetherdissolved therein to provide intimate contact between the fluorine ofsuitably small bubble size and the polymer while the solvent isvigorously being agitated. Fluorine gas may be brought into the reactionalone or together with an inert gas. Preferably, during the initialstages of the reaction the concentration of the fluorine is maintainedat a relatively low level to control the rapidity of the fluorination.As the reaction proceeds, the concentration of the fluorine gas may beincreased. Since hydrogen fluoride (HF) is produced as a by-product andgives rise to HF handling problems and polyether decomposition,fluorination of the polyethers can be advantageously carried out in thepresence of a HF scavenger, such as sodium fluoride and potassiumfluoride. The scavenger is not ordinarily soluble in the fluorocarbonfluid and is slurried in the solvent as a powder or other comminutedparticles. Although it is important that a scavenger be used since itwill react with the by-product hydrogen fluoride to minimize thereactive presence thereof, it is not essential to the carrying out ofthe process of the present invention.

Since direct fluorination reactions are highly exothermic, care is takento adequately cool the reactants while the reaction is occurring. Directfluorination of the polyethers in an inert solvent can take place in avariety of corrosion resistant reactors, such as rotating drum reactors,stirred autoclaves, and the like .

Care must be taken in the selection of the material of construction ofthe container in which the reaction takes place such that the containeror its products of corrosion do not provide for the presence of anycompound that would initiate or catalyze an adverse reaction resultingin excessive decomposition of the solvent.

One material for making a suitable reaction vessel is anickel-molybdenum-chromium wrought metal alloy which exhibits resistanceto the process environment of the present invention and does not providea source of contaminants that would initiate or catalyze decompositionof the inert solvent. A preferred corrosion-resistant alloy is onecomposed of more than fifty percent of nickel, about 15% of molybdenum,about 15% of chromium, together with minor amounts of other metals suchas Co, W, Fe, Si and Mn. One suitable alloy is sold as Hastelloy alloyC-276.

Finally, the perfluorinated polyethers are separated from the reactionmixture.

The present invention provides the advantages of producing perfluoropolyethers by a direct fluorination process and of significant reductionof reaction time by using a solvent reaction medium. While directfluorination processes are known, carrying out such process using asolvent for both the polyether and the perfluorinated polyether reactionprocess has not heretofore been successful. Another advantage of thepresent invention is that perfluorinated polyethers of a molecularweight range of about 250 to 2000 are conveniently provided in a directmanner rather than by cleaving perfluorinated polyethers of highmolecular weights.

The novel perfluorinated polyethers, dimers thereof, cyclic compoundsthereof resulting from intramolecular carbon to carbon coupling, andmixtures thereof, alone or dissolved in a solvent as herein disclosedare useful as functional fluids, including lubricants, vacuum pump oils,and heat exchange agents. Perfluorinated polyethers boiling in the rangeof about 130-330° C. are especially useful in vapor phase solderingapplications.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic block diagram showing one form of apparatus usefulfor practicing the invention.

FIG. 2 is a cross section elevational view of a reactor for convenientlycarrying out the fluorination of polyethers in accordance with thepresent invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides the manufacture of useful perfluorinatedpolyethers having a molecular weight range of about 250-2000, many ofwhich are believed to be novel, and the manufacture of certain usefuldimers of perfluorinated polyethers, and the manufacture of cycliccompounds thereof resulting from intramolecular carbon to carboncoupling, which are also believed to be novel. The perfluoropolyethersof the present invention can be represented by the following abbreviatedformula

    R.sub.f O--(CF.sub.2 CF.sub.2 O).sub.n --R'.sub.f

In this formula n represents an integer of about 1-11 and each of R_(f)and R'_(f) is independently selected from perfluorinated C₁ -C₅ alkylradicals including perfluoromethyl, perfluoroethyl, perfluoropropyl,perfluoroisopropyl, perfluorobutyl, perfluoroisobutyl, andperfluoro-t-butyl. Preferred R_(f) and R'_(f) radicals areperfluoromethyls. The perfluorinated polyethers also may be carbon tocarbon intramolecularly coupled cyclic derivatives of the just-mentionedlinear perfluorinated polyethers. Cyclic derivatives are represented bythe formulas ##STR1## wherein R_(f) and R'_(f) are as above described;R"_(f) and R'"_(f) are perfluoroalkylene groups corresponding to R ₅ andR'_(f) ; w=3 to 11, inclusive, and x+y+z=1 to 9, inclusive.

Commonly, perfluoromethyl polyethylene oxides are known asperfluoropolyglymes. This term does not precisely follow an officiallyrecognized chemical nomenclature system but is based on glymes beingused to refer to polyethylene glycols terminated with methyl groups. Onthis basis CH₃ O--(CH₂ CH₂ O)₆ --CH₃ is named hexaglyme and CH₃ O--(CH₂CH₂ O)₇ --CH₃ is named heptaglyme. When heptaglyme is fully fluorinated,the resulting product is known as perfluoroheptaglyme and has theformula CF₃ O--(CF₂ CF₂ O)₇ --CF₃, and may be abbreviated PFHG. Moreproperly, PFHG can be named1,1,1,3,3,4,4,6,6,7,7,9,9,10,10,12,12,13,13,15,15,16,16,18,18,19,19,21,21,22,22,24,24,24-tetratriacontafluoro-2,5,8,11,14,17,20,23-octaoxatetracosane. This compound and compositionscontaining the compound in a solvent therefore are new and are useful asfunctional fluids, such as lubricants and heat transfer agents.

In addition to PFHG other perfluoroethylene glycol ethers includeperfluorotriglyme, perfluorotetraglyme, perfluoropentaglyme,perfluorohexaglyme, perfluorooctaglyme, perfluorononaglyme,perfluorodecaglyme, perfluoroundecaglyme, etc. Instead of beingterminated with two perfluoromethyls, the same perfluorinatedpolyethylene glycol backbone can be terminated (i.e. R_(f) and R'_(f))with perfluoroethyl, perfluoropropyl, perfluoroisopropyl,perfluorobutyl, perfluoroisobutyl, perfluoro-t-butyl, etc. The R_(f) andR'_(f) radicals may be the same or different.

The present invention also provides for the production of an isomericmixture of dimers of PFHG. Such dimers are given the common name ofdiperfluoroheptaglyme or more properlyhexahexacontafluorohexadecaoxadotricontane. The diperfluoroheptaglymeisomers can be represented by the following formulas ##STR2## where mand n may vary from 0--6 ##STR3## where m may vary from 0-6. ##STR4##

In the direct fluorination of heptaglyme dimers thereof are produced viaradical coupling reaction. The carbon to carbon radical coupling thatproduces the dimers may occur two or more times generating cyclicperfluoropolyethers of corresponding longer chains. The additionalcouplings may occur in an end to end arrangement or between sets ofethylene carbons. The following structure represents an example os suchcoupled dimers but does not include all possible structures since crosslinking may occur at either of the ethylene carbons ##STR5## whereina+b+c+d+e+f=0 to 12, inclusive.

The direct fluorination of polyethers to produce PFHG monomer and dimersby the present process can be depicted by the following equation

    CH.sub.3 --(OCH.sub.2 CH.sub.2).sub.7 --OCH.sub.3 +34 F.sub.2 →CF.sub.3 --(OCF.sub.2 CF.sub.2).sub.7 --OCF.sub.3 +dimers+34 HF.

Where a HF scavenger, for example sodium fluoride, is used to obviatethe problems of handling hydrogen fluoride, the process can be depictedby the following reaction

    CH.sub.3--(OCH.sub.2 CH.sub.2).sub.7 --OCH.sub.3 +34 F.sub.2 +34 NaF→CF.sub.3 --(OCF.sub.2 CF.sub.2).sub.7--OCF.sub.3 +dimers +34 NaHF.sub.2

The reaction of perfluorination of polyethers is very exothermic. Forexample, the heat of reaction of preparing PFHG in accordance with thepresent invention is 4427 kcal/mol of heptaglyme. This means that tominimize the formation of unwanted reaction products, the reactionmedium should normally be positively cooled by the use of heatexchangers or the like.

In one preferred embodiment of the present invention, a reactorconstructed of a suitable metal alloy, such as Hastelloy-C is chargedwith heptaglyme or other suitable precusor polyether and a slurry ofsodium fluoride scavenger and an inert solvent for the polyether. Asindicated above the preferred solvent is1,1,2-trifluoro-1,2,2-trifluoroethane. Other suitable solvents maylikewise be employed. The resulting mixture is vigorously agitated. Theair in the reactor is purged with nitrogen to remove oxygen which mayinterfere with the reaction resulting in unwanted by-products. Thereactor mixture is maintained at a desirably low temperature. Thefluorine gas is bubbled below the level of the solvent containing thepolyether at a point of significant agitation. The fluorine is initiallydiluted with nitrogen with the concentration of the nitrogen beingreduced and the concentration of the fluorine correspondingly increased.Fluorination continues until fluorine no longer is consumed but breaksthrough the reaction mixture unreacted at which time the need forcooling is reduced. The reaction mass is filtered to remove sodiumfluoride and sodium bifluoride. The solvent is then separated by aconventional operation, such as distillation. At this point thefluorination of the polyether may be only about 90% complete. Tocomplete the fluorination the partially fluorinated polyether with orwithout HF scavenger is heated in the presence of fluorine gas at anelevated temperature, for example up to about 150° C. At this point thefluorinated polyether may contain some acyl fluoride end groups. Theseend groups are preferably eliminated by polishing the products atelevated temperatures of 150-250° C. or higher and pressures of up to300 psig or higher in the presence of fluorine for a sufficient lengthof time.

Instead of completing the fluorination and acyl end group conversion inseparate steps, both chemical conversions can be carried out in a singleoperation. In a single operation increased degradation of reactants toundesired products is more likely to be experienced.

Preferred HF scavengers include alkali metal fluoride, more preferablysodium fluoride or potassium fluoride. Calcium carbonate, sodiummonofluorophosphate, alkali metal fluorophosphate, etc. may also be usedas useful HF scavengers.

With reference now to FIG. 1 of the attached drawing numeral 1 denotes afluorination reactor whose structure is given in more detail in FIG. 2.Solvent is supplied to the reactor 1 via line 2 from a suitable sourceof sol- vent. Polyether is supplied to reactor 1 via line 3 from asuitable source of polyether. A HF scavenger is supplied to reactor 1via line 4 from a suitable source of scavenger. Fluorine gas is suppliedto reactor 1 via line 5 from a suitable source of fluorine gas. Nitrogenor other suitable inert gas is supplied to reactor 1 via line 6 from asuitable source of inert gas.

In operation, reactor 1 is charged with polyether, solvent andoptionally HF scavenger; and high speed agitation is begun. Air ispurged from the reactor with nitrogen or other inert gas. This is doneto remove oxygen which might interfere with the reaction by addingoxygen to the organic radicals that are generated causing a reducedfluorine uptake. Otherwise, there would be produced a contaminatedproduct. The reaction temperature is reduced and controlled by employingan efficient internal cooling coil or the like. During fluorination thegenerated heat of reaction is significant and is removed. Fluorine isintroduced at a point near where an effective agitating means islocated. In the initial stages of the reaction fluorine is normallydiluted with nitrogen or other inert gas. When the reaction nearscompletion, fluorine is emitted in rapidly increasing quantities as anoff gas and leaves reactor 1 via line 7 and passes through an off gasmonitoring device not shown, wherein fluorine is converted to oxygen andthe oxygen concentration is measured. By-product HF is reacted with thescavenger, if one is used. When breakthrough of the flourine gas isdetected, the reaction is discontinued. At this stage the polyether mayhave about 90% of its hydrogens exchanged for fluorines.

The reaction mass is passed via line 8 through a filter 9 to removesolid products resulting from the use of the scavenger. The solids maybe washed with solvent supplied via line 10 and then removed throughline 11. After filtration, the liquid partially fluorinated polyether ispumped through line 12 to a stripper column 13, wherein the solvent andentrained gases are stripped overhead. The gases are removed via line15. The solvent is condensed by condenser 16 and may be returned to thesystem for reuse via line 17.

Heat treatment of the reaction mass is completed in a heat treatmentreactor 18 to provide the exchange of any residual hydrogens withfluorines to produce a perfluorinated oil. The partially fluorinatedpolyether is pumped from column 13 to reactor 18 via line 19. Fluorinegas is introduced into reactor 18 through a line 20 from a suitablesource. Exchange of remaining hydrogens with fluorine may require theuse of elevated temperatures. In the early stages of heat treatmentresidual solvent may be flashed and removed from the reactor 18 via line21.

Reactor 18 is preferably equipped with agitation and heating means. Thereactor is preferably constructed of Ni--Mo--Cr metal alloy as describedmore particularly above. HF scavengers may be added to reactor 18 duringheat treatment via line 21a, if desired. The heat treated product leavesreactor 18 via line 22. When a HF scavenger is used during the heattreatment, the product is passed through a filter 23 to remove thesolids from the liquid stream. Next, the heat treated product is passedthrough a polishing reactor 24 wherein any terminal acyl fluoride groupsof the perfluorinated polyether are eliminated. This polishing isaccomplished by heating the product at a temperature and pressuregreater than that employed during the heat treatment in reactor 18 andin the presence of fluorine supplied to reactor 24 via line 25. Thepolished perfluoropolyester preferrably is next subjected to a carbontreatment in a vessel 27. Gaseous products resulting from the carbontreatment are vented from the system via line 28. From the carbontreatment the perfluropolyester is moved via line 30 to a fractionationcolumn 31, wherein the desired perfluoropolyether is separated via line32 from the remaining heavy oil. In condenser 33 the desiredperfluoropolyether is condensed and is removed via line 34. Lowerboiling perfluoropolyethers are removed via line 35. The high boilerscomposed mainly of perfluoropolyether dimers are removed via line 36.The yield of perfluoropolyether may be 90% or higher of theoretical witha 70% perfluoropolyether monomer and 30% perfluoropolyether dimer ratioresulting.

With reference now to FIG. 2 there is shown a flourination reactorsuitable for carrying out the invention. The reactor generally denotedby numeral 1 is equipped with a high speed stirrer 40 having a blade 41to effect efficient gas-liquid interfacing. High speeds of above 800rpm, preferably 1200-1400 rpm, are used due to the relatively lowsolubility of fluorine in the reaction medium. The fluorine/nitrogenfeed gas is introduced into the reactor through conduit 42 and isemitted through fine holes circumferentially disposed in a ring conduit43 located around the top tapered portion of the stirrer blade. Insteadof a ring conduit, gas may be emitted through other gas dispersionequipment, such as porous metal frits. Preferably, there are producedfine gas bubbles less than about 10 microns in diameter when the gas isinjected into the reaction mass. This small bubble size aids inmaintaining a high fluorine re action rate in the solvent of lowfluorine solubility. With the mechanical action of the high speedagitation blade and together with the small gas bubbles a satisfactoryhigh reaction rate can be maintained.

Direct fluorination of polyethers is very exothermic and thereforegenerates substantial amounts of heat. For example, the directfluorination of heptaglyme in the presence of sodium fluoride as ahydrogen fluoride scavenger produces 4427 kcal/mole of heptaglymereacted. To complete the reaction with a high degree of productivity andlow by-product formation a high surface area internal heat exchanger 44is used to provide a high coolant flow. The exchanger also may serve asa baffle for mixing enhancement. The heat of reaction is removed and thereaction temperature is controlled by this internal heat exchanger. Asillustrated, the reactor may also be provided with a jacket 45 foradditional heat removal by means of a coolant flowing through thejacket. The rapid transfer of heat from the reactants, the high speedagitation of the reactants, and the use of an inert solvent provides forfluorine addition rate several times, at least 3-5 times, the rates thatwhich are typically obtained in known direct fluorination techniques.

The following example describes a preferred embodiment of the invention.Other embodiments within the scope of the claims herein will be apparentto one skilled in the art from consideration of the specification ofpractice of the invention as disclosed herein. It is intended that thespecification, together with the example, be considered exemplary onlywith the scope and spirit of the invention being indicated by the claimswhich follow the example. Specifically, in the following examples theimprovement in manufacturing PFHG and its dimers has been demonstrated.The method employed to produce such substances can also obviously beused to produce similar perfluorinated polyethers from correspondingpolyethers.

Thus, included in the process of the present invention are thecompounds: perfluorinated glyme, perfluorinated diglyme, perfluorinatedtriglyme, perfluroinated tetraglyme, perfluorinated pentaglyme,perfluorinated pentaethylene glycol methylethyl ether, perfluorinatedpentaethylene glycol diethyl ether, perfluorinated hexaglyme,perfluorinated hexaethylene glycol methylethyl ether, perfluorinatedhexaethylene glycol diethyl ether, perfluorinated heptaglyme,perfluorinated heptaethylene glycol methyethyl ether, perfluorinatedheptaethylene glycol diethyl ether, perfluorinated octaglyme,perfluorinated octaethylene glycol methylethyl ether, perfluorinatedoctaethylene glycol diethyl ether, perfluorinated nonaglyme,perfluorinated nonaethylene glycol methylethyl ether, perfluorinatednonaethylene glycol dimethyl ether, perfluorinated decaglyme,perfluorinated decaethylene glycol methylethyl ether, perfluorinateddecaethylene glycol diethyl ether, perfluorinated undecaglyme, dimersthereof and intramolecular carbon to carbon coupled cyclic derivativesof both the monomers and dimers.

In the example all weights are given on a weight basis unless otherwiseindicated.

EXAMPLE

A five liter reactor was charged with 250 gm of heptaglyme and a slurryof 1,110 gm of sodium fluoride in 4 liters of1,1,2-trichloro-1,2,2-trifluoroethane (Freon-113). The reactor wasconstructed of Hastelloy alloy C-276 having a chemical composition ofabout 60% Ni, 15% Mo, 14.5% Cr, 3.0% W, 2.5% Co, 4.0% Fe and minoramounts of Si, Mn, C, V, p and S. Stirring was begun and maintainedduring the reaction at 1200 rpm. Air was purged from the reactor withnitrogen. By means of circulating coolant, the reaction mass temperaturewas reduced to 15° C. Thereupon, small bubbles of fluorine wereintroduced into the reactor using a multiported ring positioned aroundthe top of the stirrer blade as illustrated in FIG. 2. The fluorine wasinitially diluted with nitrogen; the flows of fluorine and nitrogen wereadjusted during the reaction as indicated in the following table.

                  TABLE 1                                                         ______________________________________                                        REACTION PROFILE                                                              Elapsed   Fluorine,     Nitrogen,                                                                              Temp.,                                       Time, Min sccm          sccm     °C.                                   ______________________________________                                         0         500          1000     15                                           10        1000          1000     15                                           20        1500          500      15                                           30        2000          500      15                                           45        2500          500      15                                           245       1000          500      25                                           255        500          500      25                                           280         0           1000     25                                           ______________________________________                                    

Total time until fluorine breakthrough was approximately four hours.Breakthrough was determined by detecting a decreased need for cooling tomaintain the desired reaction temperature. A sharp increase in theamount of unreacted fluorine leaving the reactor was determined byfollowing the percent of oxygen in the off gas. This also signaledbreakthrough of the fluorine. The reaction off gas passed through analumina trap reactive with fluorine to produce the oxygen. Bydetermining the amount of oxygen displaced by the fluorine, one is ableto determine quantitatively the amount of fluorine being passed through.As the breakthrough occurred, fluorination at a reduced rate wascontinued for an additional 35 minutes; and the reaction temperature wasraised to about 25° C. Thereafter the fluorine feed was discontinued.The reaction mass was agitated for an additional 15 minute period with anitrogen purge to eliminate any dissolved fluorine. The heptaglyme atthis stage had 90-95% of its hydrogens exchanged with fluorines. Thefluorine usage in the reaction step was about 110% of theoretical. Thereaction mass was filtered and the solvent was stripped from the oil bydistillation to provide 634 g of fluorinated oil.

Masses of several fluorination reactions were combined for feed to thesubsequent process steps.

A five-liter heat treatment vessel was charged with 7105 g of thefluorinated PFHG oil and 300 g of sodium fluoride. Air was purged fromthe reactor with nitrogen. The 5-10% remaining hydrogens on thesubstantially fluorinated heptaglyme were exchanged for fluorines byreacting the crude oil with fluorine at a temperature in the range of31-128° C. at atmospheric pressure and with vigorous agitation. The flowrates of fluorine and nitrogen were adjusted during the reaction asindicated in Table 2 which follows.

The mixture was filtered affording 6676 g oil. The solids were washedwith solvent. The solvent was removed affording an additional 209 g ofoil. A second washing with solvent afforded an additional 116 g of oil.A total of 7001 g (95% of charge) of oil was recovered.

                  TABLE 2                                                         ______________________________________                                        REACTION PROFILE                                                              Elapsed   Fluorine,     Nitrogen,                                                                              Temp.                                        Time, Min sccm          sccm     °C.                                   ______________________________________                                         0         500          1000      31                                          10        1000          1000      59                                          15        1000          500       70                                          20        1500          250       86                                          30        1500          250      108                                          45        2000          250      113                                          60        2500          250      118                                          80        3000          250      128                                          132       2000          250      127                                          137       1000          250      120                                          155       1500          250      113                                          168       1500           0       113                                          177         0            0       112                                          ______________________________________                                    

Final polishing was accomplished as follows.

A two liter polishing vessel was charged with 1564 g of heat treatedproduct. The product was stirred at 300 rpm and brought into reactivecontact with fluorine. The flow rates of fluorine and nitrogen and thetemperature and pressure of the autoclave were adjusted during thereaction as indicated in the following table.

                  TABLE 3                                                         ______________________________________                                        REACTION PROFILE                                                              Elapsed    Fluorine,                                                                              Nitrogen,   Temp.,                                                                              Press                                   Time, Min  sccm     sccm        °C.                                                                          psig                                    ______________________________________                                         0         0        15           29   0                                       69         20       15          125   0                                       71         100      0           130   0                                       80         200      0           155   0                                       95         200      0           165   0                                       143        0        0           236   95                                      170        0        0           250   90                                      230        0        0           253   90                                      ______________________________________                                    

A total of 1505 g (96% of charge) of polished oil was recovered from thereactor.

The thus polished product was refined by distillation to yield a PFHGoverhead product and a PFHG dimers bottoms product.

Heat treatment and polishing of the recovered oil, respectively,completed the exchange of residual hydrogens with fluorines andeliminated acyl fluoride groups generated by cracking.

The following properties of PFHG and dimmers were measured and have beenset forth in the following table.

                  TABLE 4                                                         ______________________________________                                        PFHG                                                                          Average Molecular Weight                                                                           1000                                                     Boiling Point, °C. @ 760 torr                                                                215                                                     Pour Point, °C.                                                                             -25                                                      Density @ 25° C. g/cc                                                                       1.72                                                     PFGH DIMERS                                                                   Average Molecular Weight                                                                           1900                                                     Boiling Point, °C. @ 4 torr                                                                  200                                                     Pour Point, °C.                                                                             -70                                                      Density @ 20° C. g/cc                                                                       1.81                                                     ______________________________________                                    

EXAMPLE 2

In this example the crude oil of Example 1 from which the solvent hadbeen stripped was heat treated and polished in one reactor without theuse of sodium fluoride scavenger or any other HF scavenger. A two-literautoclave reactor was charged with 1967 g of the oil. The oil wasstirred at 1000 rpm and brought into reactive contact with fluorine. Theflows of fluorine and nitrogen and the temperature and pressure of thereactor were adjusted during the reaction as indicated in the followingtable.

                  TABLE 5                                                         ______________________________________                                        REACTION PROFILE                                                              Elapsed    Fluorine,                                                                              Nitrogen,  Temp.,                                                                              Press.,                                  Time, Min. sccm     sccm       °C.                                                                          psig.                                    ______________________________________                                         0         0        50          24   0                                         31        50       15          50   0                                         50        200      15          70   0                                         75        400      15         100   0                                        365        50       0          128   0                                        380        200      0          137   0                                        415        0        0          157   80                                       The reactor was cooled for sampling.                                           0         200      0           31   0                                         33        0        0           35   80                                       153        0        0          249   90                                       213        0        0          250   90                                       The reactor was cooled for sampling.                                           0         200      0           85   0                                         27        0        0          109   80                                        96        0        0          250   112                                      156        0        0          251   112                                      ______________________________________                                    

A total of 1884 g (96% of charge) of polished oil was recovered.

What is claimed is:
 1. Perfluoroheptaglyme dimer.